1. Field of the Invention
The present invention relates generally to oscillatory apparatus for use in sensing applications, and more particularly in one exemplary aspect to an inertial time domain sensing apparatus, and methods of utilizing the same.
2. Description of Related Technology
Accurate measurements of parameters (such as for example force) are often required in a wide variety of applications. Micro-electromechanical sensors (MEMS) devices such as accelerometers have been extensively used in, e.g., dynamic distance and speed measurements, inclination, machine vibration, buildings and structural monitoring, component placement in manufacturing, process control systems and safety installations. Angular rotation rate MEMS (also referred to as the gyroscope or the rate sensors) are useful in, inter alia, navigation, automotive (e.g., electronic stability control), entertainment (e.g., user motion detection for game consoles), photography (e.g., image stabilization), animal behavior studies and many other applications. Pressure sensors are similarly widely used in applications such as weather, industrial monitoring and control, aircraft and automotive, oil and gas exploration, flow sensing, acoustics, etc. Many other parameter measurement applications exist (such as for example, magnetic force measurements used in navigation and mineral exploration, or electrostatic force measurements used in microscopy, etc.).
However, most presently available inertial sensors of sufficient resolution for a given application are costly, thereby limiting their use and widespread adoption. Conversely, more inexpensive inertial sensor solutions currently available do not provide sufficient accuracy and stability required for many applications, such as industrial measurement. Existing sensor solutions (whether of the more costly or more inexpensive variety) also require periodic recalibration and dedicated signal conditioning circuitry, and are generally susceptible to noise interference, thus limiting installation flexibility.
Yet another drawback of these prior art solutions relates to their limited dynamic range; generally speaking, two or more separate sensors are required for sensing or measurement of parameter values of significantly different amplitude, thereby further increasing the cost and complexity of systems capable of measurement over wide dynamic ranges.
In the context of a force measurement, the typical prior art force sensor measures displacement (also often referred to as “deflection”) of a spring-suspended proof mass in order to estimate a force acting on the proof mass. The methods of measuring such deflection vary in accuracy, variability, and cost of implementation. Various measurement approaches may be used, such as for example capacitive, piezo-resistive, electron tunneling sensing, and optical interferometry, in order to determine the proof mass deflection. In all of these approaches, the deflection (and thus the force) is inferred as a function of a measured voltage (or electric current), and therefore is inevitably subject to measurement errors due to, inter alia, thermal and electromagnetic noise. As a result, most existing force sensor solutions require very accurate signal conditioning circuitry (such as precision amplifiers, filters, voltage references, etc.), as well as periodic recalibrations to account for sensor aging (including e.g., changes in the physical properties or characteristics of the “spring” and/or proof mass with time), and electrical component drift. In the case of force sensors utilizing electron tunneling tips, tunneling can occur at several points along the motion of the tunneling tip—resulting in noise being added to the system.
Accordingly, there is a salient need for an improved high-accuracy and high-resolution force sensing apparatus having an increased dynamic range, that at the same time is both lower in cost and complexity as compared to existing solutions. Ideally, such improved sensing apparatus would also mitigate or completely obviate the need for calibration (i.e., be “self-calibrating”), and could be used in a wide variety of parametric sensing, measurement, or other applications.